The invention relates to apparatus for separating particles differing in specific gravity by means of a liquid separating medium, using the float-and-sink method, the apparatus comprising a washing tank with means movable along its bottom for removing the settled particles and with means for removing the floating particles.
Apparatus of this kind is known, for instance, from the British Patent Specification No. 868,832. In this apparatus the means for removing the settled particles which move along the tank bottom take the form of a scraper chain. For the purpose for which this known apparatus was designed, viz. separating useful minerals from rock, more in particular separating coal from shale, this is very satisfactory. However, it is not so if the material to be separated according to specific gravity tends to get tangled in itself and to cling to the scraper chain so that this can jam. Such a difficult-to-work material is, for instance, the scrap coming from shredders in which wrecked or disused cars, disused domestic appliances, etc. are disintegrated. The ferromagnetic components of the scrap leaving the shredder are generally separated from the non-ferromagnetic components by means of a magnetic separator. The non-ferromagnetic part of the scrap contains components widely differing in sepcific gravity, e.g. non-metals, such as plastics, wood and rubber, lighter metals and alloys, such as aluminium and aluminium alloys, and heavier metals, such as copper, lead, stainless steel, etc. It is the object of the invention to provide float-and-sink apparatus of the type described above which can, without objection, also be used for separating such a difficult-to-handle material according to specific gravity.
According to the invention, the said means movable along the bottom of the washing tank for removing the settled particles can be moved between two extreme positions so that during the movement from at least one of the extreme positions to the other extreme position they can transport settled particles across the edge of the washing tank to a discharge point.
According to the invention, the said means for removing the settled particles preferably comprise at least one collecting tray that can be reciprocated along the bottom of the washing tank, which collecting tray in the first extreme position is about centrally on the bottom of the washing tank where it can collect settling particles, and in the second extreme position rests on the edge of the washing tank, so tilted that the settled particles contained in it can slide into a discharge device positioned next to the washing tank, for which purpose the collecting tray is open at the discharge side. In addition, there may be a collecting plate moving along with the collecting tray, on which plate particles settling during the travel of the collecting tray are collected, and across which these particles can slide into the collecting tray when this is travelling back to its starting position. By preference the apparatus is provided with a second collecting tray that can move, in a similar way as described for the first collecting tray, between two extreme positions, and which rests about centrally on the bottom of the washing tank when the first collecting tray has reached its tilted position on the edge of the washing tank, and rests tilted on the opposite edge of the washing tank when the first collecting tray is approximately centrally positioned on the bottom of the washing tank. This second collecting tray can likewise cooperate with a collecting plate as described above.
According to the invention, the mechanism reciprocating the collecting trays with the collecting plate (if present) between the extreme positions is preferably so designed that the collecting trays are hingingly attached to one or more arms fixed on a horizontal shaft provided with driving means for swinging to and fro between two extreme positions the shaft with the arms and the collecting trays hingingly attached to them. If a collecting plate is used, this is preferably also attached to the said arm(s).